COM and SEG drivers with 4 to 5 voltage levels CL1, CL2, D and M lines for external drivers. where CL1, CL2, D and M are: The display panel is organized in rows driven by the controller COMs, while columns are driven by controller or auxiliary driver SEG lines. The driving scheme for passive matrix displays depends on the arrangement of character groups and format (e.g. 5x8, 5x10, 5x11), but is most often seen to be 1:16-multiplexed with 1/5 level bias. The 1:2 multiplex scheme below (taken from the NXP PCF2119 datasheet) conveys the idea in a more accessible fashion. STN pixels at the junction of row and column conductor stripes see a differential AC waveform. Small amplitudes don't cause a pixel to switch, and in this case, pairs of frames must be generated complementarily to create a zero time average (no DC component).